Pyrrolo[2,1-c][1,4]benzodiazepine antitumour antibiotics are commonly known as anthramycin class of compounds. In the last few years, a growing interest has been shown in the development of new pyrrolo[2,1-c][1,4]benzodiazepine (PBDs). These antibiotics react covalently with DNA to form an N2-guanine adduct that lies within the minor groove of duplex DNA via an acid-labile aminal bond to the electrophilic imine at the N10-C11 position (Kunimoto, S.; Masuda, T.; Kanbayashi, N.; Hamada, M.; Naganawa, H.; Miyamoto, M.; Takeuchi, T.; and Unezawa, H. J. Antibiot., 1980, 33, 665.; Kohn, K. W. and Speous, C. L. J. Mol. Biol., 1970, 51 551.; Hurley, L. H.; Gairpla, C. and Zmijewski, M. Biochem. Biophys. Acta., 1977, 475, 521.; Kaplan, D. J. and Hurley, L. H. Biochemistry, 1981, 20, 7572). The molecules have a right-handed twist, which allows them to follow the curvature of the minor groove of B-form double-stranded DNA spanning three base pairs. Recently, PBD dimers have been developed that comprises two C2-exo methylene substituted DC-81 subunits tethered through their C-8 position via an inert propanedioxy linker (Gregson, S. J.; Howard, P. W.; Hartley, J. A.; Brooks, N. A.; Adams, L. J.; Jenkins, T. C.; Kelland, L. R. and Thurston, D. E. J. Med. Chem. 2001, 44, 737). A recent development has been the linking of two PBD units through their C-8 positions to give bisfunctional alkylating agents capable of cross-linking DNA (Thurston, D. E.; Bose, D. S.; Thomson, A. S.; Howard, P. W.; Leoni, A.; Croker, S. J.; Jenkins, T. C.; Neidle, S. and Hurley, L. H. J. Org. Chem. 1996, 61, 8141).

A non-cross-linking mixed imine-amide PBD dimers have been synthesized that have significant DNA binding ability and potent antitumour activity (Kamal, A.; Ramesh, G. Laxman, N.; Ramulu, P.; Srinivas, O.; Neelima, K.; Kondapi, A. K.; Srinu, V. B.; Nagarajaram, H. M. J. Med. Chem. 2002, 45, 4679). Recently, some new pyrrolobenzodiazepine (PBD) hybrids have been synthesized that have significant DNA binding ability and potent antitumour activity (Kamal, A.; Srinivas, O.; Ramulu, P.; Ramesh, G.; Kumar, P. P. Bioorg. Med. Chem. Lett. 2003, 13, 3577).
Naturally occurring pyrrolo[2,1-c][1,4]benzodiazepines belong to a group of antitumour antibiotics derived from Streptomyces species. Recently, there is much impetus for the PBD systems as they can recognize and bind to specific sequence of DNA. Examples of naturally occurring PBDs include anthramycin, DC-81, tomaymycin, sibiromycin and neothramycin.
Phenanthrylphenol is small synthetic molecule that contains a phenanthrene ring coupled to a 4-hydroxy phenyl boronic acid (Suzuki cross-coupling reaction). A number of polyaromatic hydrocarbons (PAH) and their derivatives in view of their planar ring system are known to intercalate with DNA resulting in the anticancer activity (Venitt, S.; Crofton-Sleigh, C.; Agbandje, M.; Jenkins, T. C.; Neidle, S. J. Med. Chem. 1998, 41, 3748. Kamal, A.; Ramsh, G.; Srinivas, O.; Ramulu, P.; Bioorg. Med. Chem. Lett. 2004, 14, 471).
The structurally related phenanthrenes have also been reported to possess anticancer activity (Jones, B. G.; Mathews, J. E.; Banner, K. W. Heterocycles, 38, 6, 1994, Wei, L.; Brossi, A.; Kendall, R.; Bastow, K. F.; Natschke, S. L. M.; Shi. Q.; Lee. K. H.; Bioorg. Med. Chem. 2006, 14, 6560. Shagufa.; Srivastava, A. K.; Sharma, R.; Mishra, R.; Balapure, A. K.; Murthy, P. S. R.; Panda, G.; Bioorg. Med. Chem. 2006, 14, 1497). Based on the potent anticancer activity of pyrrolo[2,1-c][1,4]benzodiazepines, phenanthrenes, new PBD hybrids have been designed and synthesized by linking phenanthrylphenol moiety at C8-position of pyrrolo[2,1-c][1,4]benzodiazepine with varying alkane spacers.